1. Field of the Invention
The present invention relates to a connecting pin for connecting elements of e.g. a chain and also a connecting method using the connecting pin.
2. Description of the Related Art
A chain such as a drive chain for use in a bicycle for operatively connecting a front gear attached to a crank shaft and a rear hub includes, as its connecting elements, a pair of inner plates each defining pin hole at opposed ends thereof and a pair of outer plates each defining corresponding pin holes at opposed ends thereof. These inner and outer plate are overlapped at their ends so as to align the respective corresponding pin holes with each other. Then, a connecting pin is forcibly inserted into the common pin hole defined by the overlapped inner and outer plate. As a plurality of inner and outer plates are connected in series with each other, there is formed one chain loop.
On some occasions e.g. for entraining the chain on a particular or different combination of a front gear and a rear gear or for eliminating unnecessary looseness of the chain which may occur through an extended period of use, the chain length must be adjusted. For such chain length adjustment, one or plurality of connecting pins (the number depends on the amount of adjustment needed) are completely withdrawn from the pin holes of the respective plates of the chain by using a pin attaching-detaching device so as to detach the corresponding plates. The, the inner plates and the outer plates at the free ends of the disconnected chain are again overlapped with each other in the manner described above and are connected by forcibly inserting the pin into the pin hole to form a new chain loop. The disconnecting operation of the chain can be alterantely effected without the complete withdrawal of the connecting pin. In this case, the pin is not completely withdrawn from the connecting hole of the plates but is withdrawn just enough to permit detachment of the plates, such that one longitudinal end of the pin is retained at the pin hole of the outer or inner plate to be maintained. With completion of a plate detaching operation, the pin which one end is retained at the hole of the outer (inner) plate is pushed, by its opposite ends, into a hole of the new inner (outer) plate to form a new complete chain loop. A chain length adjustment for increasing the chain length can be effected in substantially the same manner as described above.
The pin attaching-detaching device used in the above operations, as illustrated in FIG. 5, includes a base member A, a control rod C attached in the base member A through a threaded engagement, the rod C having a pin push shaft B at a terminal end thereof, and a chain receiving portion E defining a receiving hole D for receiving the pin push shaft B. In operation, an outer face of an outer plate pair to be disconnected form the chain is fitted to an end face of the chain receiving portion E. In this condition, the control rod C is operated, i.e. rotated to cause a leading end of the pin push shaft B to come into contact with an end face of the connecting pin. As the rod C is further rotated, the push shaft B pushes the connecting pin out of the pin hole of the outer plate pair and the inner plate pair aligned therewith. With completion of necessary chain length adjustment as described above, the withdrawn (completely or partialy withdrawn) pin is again used for connecting a new pair of inner and outer plates.
However, if the chain length adjustment is carried out by using the above-described pin attaching-detaching device without complete withdrawal of the connecting pin, an operator feels it very difficult to determine the withdrawal amount of the pin just enough for plate detachment.
Further, since the pin push shaft B moves into the pin hole from which the pin has been withdrawn, the operator can know whether or not the pin has been withdrawn by a proper amount for the plate detachment only after releasing the control rod therefrom. For this reason, an inexperienced operator often has to repeat the operation in a trial and error manner. With either complete or partial withdrawal of the connecting pin, the chain connecting operation after the chain length adjustment has been very troublesome and time-consuming.
Moreover, when the pin is withdrawn form the pin hole, this withdrawal motion can damage the pin through the friction associated therewith. Accordingly, even if the pin can be successfully inserted into the hole again, the damaged pin may not be retained at the pin hole properly or sufficiently, and an inadvertent pin detachment tends to occur after the chain length adjustment.
The present invention attends to the above drawbacks of the prior art. And, the primary object of the invention is to provide an improved connecting pin and connecting method using this pin which permits easier pin connecting operation and more reliable connection after the operation.